1. Field of the Invention
The invention relates to a cold pilger rolling tool for producing internally ribbed tubes using the cold pilger step rolling process in a rolling stand which is movable back and forth in the direction of rolling and has rolls which are of tapered design and roll along the material to be rolled with an alternating direction of rotation, the tool including a cold pilger rolling mandrel which also tapers.
2. Description of the Related Art
For certain applications such, for example, as for improving the transfer of heat and flow conditions in heat exchangers and pipes, tubes are required to have an internal surface with helical ribbing for guiding the flow therethrough. For these applications, the ribbing is preferably fine-toothed such, for example, as having 60 ribs at a lead angle of approximately 20.degree. the ribbing preferably has a relatively small depth.
Suitable materials for these pipes and tubes which require the internal ribbing include all metallic materials, including steel.
The helical internal ribbing for copper material pipes and tubes has been produced in drawing lines using a suitably helical drawing mandrel.
This method of producing the internal ribbing in drawing lines is applicable to relatively soft materials and thin-walled tubes such, for example, as copper tubes. However other materials which are difficult to form can only be ribbed to a limited extent or with a simple rib geometry.